Transmission of moving pictures in real-time is employed in several applications e.g. video conferencing, net meetings, TV broadcasting and video telephony.
A conventional videoconferencing end-point includes a camera lens system rotary connected to a camera base for capturing a scene of interest, such as the environs adjacent table as well as conference participants themselves. The camera lens system is typically connected to the camera base in a manner such that the camera lens system is able to move in response to one or more control signals. By moving the camera lens system, the view of the scene presented to remote conference participants changes according to the control signals.
Further, the camera lens system may pan, tilt and zoom in and out. “Pan” refers to a horizontal camera movement along an axis (i.e., the X-axis) either from right to left or left to right. “Tilt” refers to a vertical camera movement along an axis either up or down (i.e., the Y-axis). “Zoom” controls the field of view (i.e., the Z-axis) of a video image by varying focal length.
A lens motor is coupled to the lens mechanism to mechanically change the field of view by “zooming in” and “zooming out”. The lens motor performs the zoom function under the control of a lens controller. The lens motor and other motors associated with the camera (i.e., tilt motor and pan motor drive) are electromechanical devices that use electrical power to mechanically manipulate the image viewed by, for example, geographically remote participants. The tilt motor and drive is included in the lens system and provides for a mechanical means to vertically move the image viewed by the remote participants.
The video image captured by the camera is displayed on a display operating on a display monitor either at the near-end and/or at the far-end side of the conference. The display monitor can be a television, computer, stand-alone display (e.g., a liquid crystal display, “LCD”), or the like and can be configured to receive user inputs to manipulate images displayed on the display.
There exist many drawbacks inherent in conventional cameras used in traditional teleconference applications. Electro-mechanical panning, tilting, and zooming devices add significant costs to the manufacture of the camera. Furthermore, these devices also decrease the overall reliability of the camera. Since each element has its own failure rate, the overall reliability of the camera is detrimentally impacted with each added electromechanical device. This is primarily because mechanical devices are more prone to motion-induced failure than non-moving electronic equivalents.
Furthermore, switching between preset views associated with predetermined zoom and size settings for capturing and displaying images take a certain interval of time to adjust. This is primarily due to lag time associated with mechanical device adjustments made to accommodate switching between preset views. For example, a maximum zoom out may be preset on power-up of a data conference system. A next preset button, when depressed, can include a predetermined “pan right” at “normal zoom” function. In a conventional camera, the mechanical devices associated with changing the horizontal camera and zoom lens positions take time to adjust to the new preset level, thus inconveniencing the remote participants.
Another drawback to conventional cameras used in video conferencing application is that the camera is designed primarily to provide one view to a remote participant. For example, if a display with two views were requested at a remote participant site, e.g. one survey picture and one zoomed picture, then two independently operable cameras thus would be required.
A participant in a face to face meeting usually changes field of view, typically by focusing on the talker, one of the listeners or trying to keep an overview of all/several participants. State of the art video conferencing equipment usually brings one image from the remote side. This image is often a scaled down version of the camera input. The drawback is of course that a quick change or switching between fields of view is not possible.
U.S. patent application Ser. No. 10/358,758 discloses a method and apparatus for digital zoom, pan and tilt within a visual angle of the camera lens by decreasing/increasing the number of captured and transferred pixels in response of a control signal from the far- or near-end. In this way the user have a feeling of controlling the camera without requiring any mechanical changes. However, the resolution of the picture section within the view of angle is still limited to the mechanical zoom of the camera, and there are no scaling apart from capturing more or less of the pixels being available from the sensors in the camera. In fact, the application merely discloses state of the art digital zoom used in video conferencing application.